I-amjnoaryl-s-pyrazolone-x



Patented Apr. 6, 1943 1 -AM]NOARYL--PYR AZOLONE-4- SULPHONIO ACIDS PaulZervas, Cologne Mulheim, Germany, assignor to General Aniline & FilmCorporation, New York, N. Y., a corporation of Delaware No Drawing.Application August 9, 1941, Serial No. 406,239. InGermany April 6, 19395 Claims.

The present invention relates to l-aminoaryl- 5-1pyrazolone-4-sulphonicacids and to a method of preparing the same.

If concentrated sulphuric acids in the presence of acetic anhydride orchlorosulphonic acid are allowed to react with 5-pyrazolones,5-pyrazolone- 4-s-ulphonic acids are obtained. The sulphonic acid groupin these pyrazolones is labile; it can be split off, for instance bymeans of hydrochloric acid or can be replaced by the nitroso group bythe action of sodium nitrite.

It has now been found that the 4-sulphonic acids of l-nitroarylor1-acylaminoaryl-5-pyrazolones prepared according to this method can bereduced or saponified to l-aminoaryl-S-pyrazolone-i-sulphonic acidsaccording to the usual methods without a splitting off of the sulphonicacid group. This fact could not be foreseen considering the labileposition of the sulphonic acid group. It has proved to be preferable toeffect the reduction in a weakly acid or alkaline medium, thesaponification in an alkaline medium. The1-aminoaryl-5-pyrazolone-4-sulphonic acids thus obtainable are of greattechnical importance as the new compounds are valuable intermediateproducts, e. g. for the manufacture of azodyestufis.

The following examples illustrate the invention without, however,limiting it thereto, the parts being by weight.

Example 1 32.1 parts of sodium 1-(l'-nitrophenyl)-3-methyl-5-pyrazolone-4-sulphonate are dissolved in 100 parts of water andreduced at 75-85" C. i

phonic acid separates as yellowish white crystals with good yield.

Example 2 32.1 parts of sodium 1-(3-nitrophenyl)-3-methyl-5-pyrazolone-4-su1phonate are dissolved in parts of water and aconcentrated solution of parts of sodium carbonate is added. Then aconcentrated solution of 170 parts of ferrous sulphate is allowed to runinto this solution at a temperature of 50-60 C. When the reduction iscomplete the precipitate of ferric hydroxide is removed by filtration.The amino compound can be separated from the filtrate as a whiteprecipitate by acidifying with hydrochloric acid.

Example 3 33.3 parts of sodium 1-(4'-acetamino:phenyl)- 3-methyl-5pyrazolone 4 sulphonate are dissolved in parts of 10 per cent causticsoda lye and saponified by heating for about 1 hour. The isolation ofthe 1-(4a minophenyl) -3'-methyl-5-pyrazolone-4-su1phonic acid iseffected by neutralizing and evaporating as stated in Example 1.

I claim:

1. Process of preparing 1-aminophenyl-5-pyrazolonei-sulphonic acidswhich comprises treating 1-nitrophenyl-5-pyrazolone-4-sulphonic acidwith reducing agents for nitro groups.

2. Process of preparing l-aminophenyl-5-pyrazolone-i-sulphonic acidswhich comprises treating a 1-nitrophenyl-5-pyrazolone-4-su1phonic acidwith a reducing agent for nitro groups in a weakly acid to alkalinemedium.

3. As new products l-aminophenyl-E-pyrazolone-i-sulphonic acids.

4. As new product 1 (4' aminophenyD-3- methyl-5- pyrazolone 4-sulphonicacid.

5. As new product 1 (3' aminophenyD-3- methyl-5-pyrazolone-4-sulphonicacid.

PAUL ZERVAS.

